Process for preparation of bis(trinitroethyl)amine



-ever, it is not practical to 3,006,957 Patented Oct. 31, 1961 3,006,957 PROCESS FOR PREPARATION OF BIS('IRINHTROETHYL)AMlNE Wallace J. Murray and Charles W. Sauer, Cambridge, Mass, assignors to Arthur D. Littie, Inc., Cambridge, Mass, a corporation of Massachusetts N Drawing. Filed Mar. 11, 1957, Ser. No. 644,990

7 Claims. (Cl. 260-583) This invention relates to a one-step process for the preparation of explosive intermediates, and particularly to a process for the preparation of bis(trinitroethyl)- amine. It is a continuation-in-part of our copending application Serial No. 290,812, and now abandoned, filed May 29, 1952.

In explosives and propellants it is necessary that the explosive or propellant, or one of its components, furnish oxygen to burn the carbon and hydrogen present. One compound, bis(2,2,2-trinitroethyl)nitramine, has been found to be an excellent oxygen-rich compound as an explosive or propellant component. The preparation of bis(2,2,2-trinitroethyl)nitramine requires bis(trinitroethyl)amine as an intermediate.

Bis(2,2,2-triuitroethyl)nitramine is particularly suited for the above-mentioned purposes where additional atmospheric oxygen is not available. There are only a few stable compounds having a positive oxygen balance. Such compounds carry within their own molecules more oxygen atoms than are required to burn the carbon and hydrogen atoms present. One of these compounds is bis(2,2,2-trinitroethyl)nitramine, which has been observed to have a ballistic mortar value of 139% TNT. Howuse such a compound having a positive oxygen balance alone. Therefore, explosives have been made up using this bis(2,2,2-trinitroethyl)nitramine with other explosives and fuels which are deficient in oxygen. For example, a mixture of this material with TNT (70/30) has been shown to have a ballistic mortar value of 148% TNT. This illustrates the value of the additional oxygen in the oxygen-rich compound to materially increase the power of the TNT. Another mixture of bis(2,2,2-trinitroethyl)nitramine with cyclotetramethylenetetranitramine (30/70) has been shown to have a ballistic mortar value of 154% TNT. Furthermore, bis- (2,2,2-trinitroethyl)nitramine is useful in connection with plastic materials used as fuels in propellant compositions.

The explosive mixtures described may be used in blockbusters or torpedeos, and in connection with metals, such as aluminum, for underwater blast and anti-aircraft shells, where afterburning is important. The additional oxygen in the bis(2,2,2-trinitroethyl)nitramine reacts with the aluminum or other metal to activate it so that it may burn very rapidly in the surrounding air.

The preparation of bis(2,2,2-trinitroethyl)nitramine is most conveniently and economically accomplished by reacting bis(trinitroethyl)amine with nitric acid in the presence of sulfuric acid in accordance with the following equation:

One object of this invention is to provide a simple process for the manufacture of the above-mentioned intermediate compound bis(trinitroethyl)amine. A further object of this invention is to provide an automatic pH control of the reactions involved. Another object of this invention is to provide a possible means of developing a continuous process for the manufacture of bis(trinitroethyl)amine. Another object is to provide a step where by greater economy in the production of the valuable oxygen-rich high explosive, bis(2,2,2-trinitroethyl)nitramine, may be attained.

These objects are accomplished by the procedure of the present invention, which is described in detail below. The process of this invention, when starting with potassium nitroform, involves forming a water-wet cake of potassium nitroform by any known process and mixing this with water and suflicient acid to liberate free nitroform in solution. To this solution is added an aqueous solution of hexamethylenetetramine. The resulting bis(trinitroethyDamine, which precipitates in crystalline form, is filtered off. The reaction proceeds as follows:

Other alkali metal salts of nitroform may be used in place of the potassium nitroform. The term alkali metal is used herein to include not only such metals as lithium, sodium and potassium, but also ammonium. The process may be started directly with a water solution of nitroform or of any alkali metal salt of nitroform prepared by any of the known methods.

Any strong mineral acid, the pH of which remains around 1 in aqueous solution, is suitable for use in this preparation in place of the hydrochloric acid specified above; e.g., nitric acid or sulfuric acid.

The alkali metal salt of nitroform should be used in a damp form, or water suspension, since the dry alkali metal salt of nitroform or nitroform itself may be easily detonated. The actua amount of alkali metal salt of nitroform present can be estimated by assaying an aliquot for calculating the quantities of the other reactants which are added. Although the reactants may be used in the molar quantities indicated in the equation above, it is preferable to add some excess of hexamethylenetetramine.

The reaction of our invention is feebly exothermic and is preferably carried out within the approximate temperature range of 20 to 30 C. If it is found desirable to react the materials at the lower temperature, it is preferable to use a cooling bath around the reaction vessel. Reaction temperatures materially lower than 20 C. slow down the reaction undesirably, while reaction temperatures materially higher than 30 C. would cause decomposition of the bis(trinitroethyl)amine to set in.

The pH of the reaction in our invention remains under 2 throughout. Since free nitroform itself has a pH of about 1.5, it would be necessary to add only a small amount of mineral acid to the reaction if free nitroform is used in place of a metal salt of nitroform. It is important to keep the pH below 2, and preferably at about 1. Excess acid does no harm while insuificient acid causes the formation of a troublesome yellow impurity.

The following examples, which are to be considered as illustrative rather than limiting, will serve to explain the present invention in more detail.

Example I In an 800 ml. beaker, equipped with a stirrer and thermo-couple well, was put the damp potassium nitroform obtained from grams of tetranitromethane (estimated to be about 40 grams of potassium nitroform on dry basis) suspended in 200 ml. of water. To this water suspension of potassium nitroform was added ml. of 20% (1:1 or 6 N) HCl, and then very slowly 7 grams of hex-amethylenetetramine dissolved in 50 ml. of water. The reaction was maintained at about 20 C. by use of an ice bath surrounding the reaction vessel. The mixture was stirred for several hours and left overnight at room temperature. The pH throughout this part of the reaction was about 1.8. After standing, the reaction mixture was cooled in an ice bath, and the precipitated material, bis- (trinitroethyDamine, was filtered off on a sintered glass filter and washed with ice water. The filtrate ordinarily has a slight odor of formaldehyde. The water-wet cake of bis(trinitroethyl) amine was digested with warm chloroform. After standing for a brief time, the mixture separated into three phases: a yellow aqueous top phase containing most of the water from the cake, a solid phase of bis(trinitroethyl)amine, and a chloroform solution.

The water phase was decanted and discarded. The bis- (trinitroethyl)amine was crystallized and recrystallized from the chloroform until the desired purity was obtained.

The final yield was about 25 grams of slightly damp crystals melting at 114 C. with decomposition. This is equivalent to about 60-70% yield based on the original 45 grams of tetranitromethane.

Example 11 It will be noted that nitroform is released by the action of HCl on the potassium nitroform. Hence, as suggested above, the procedure of this invention may be carried out by starting directly with nitroform dissolved in Water and using the molar quantities (with a slight excess of hexamethylenetetramine) indicated by the following equation:

The preparation then proceeds as in the above Example I. The pH of the reaction is below 2.

The procedure set forth in Example I involves the reaction between potassium nitroform, mineral acid, and hexamethylenetetramine in an aqueous medium. Although it has been found convenient to add these reactants in the order described, they may be mixed together at one time or in any desired order.

The steps set forth in Example I for recovering the bis(trinitroethyl) amine formed in the reaction are intended to give a high yield of pure product. They may, however, be varied as desired, since other washing and recovery prowdures are possible. Although chloroform is used, other recrystallization solvents may be used equally well.

The simple addition of these reactants in an aqueous medium and the automatic control of pH in the condensation step make it possible to adapt this method of bis(trinitroethyl)amine preparation to a continuous process. For example, suitable quantities of potassium nitroform and hexamethylenetetramine in aqueous medium and HCl may be simultaneously and continuously introduced into a reaction vessel, continuously stirred and maintained at a suitable reaction temperature. Periodically, the reaction mixture could be withdrawn, further agitated in a tank, and then the bis(trinitroethyl)amine separated out in a manner such as that shown in Example I.

We claim:

1. A process for making bis(trinitroethyl) amine which comprises preparing an aqueous suspension of a nitroform compound having the formula MC(NO wherein M is a member of the group consisting of H, Li, Na, K, and NH mixing said nitroform compound suspension with hexamethylenetetramine in a ratio of six moles of nitroform compound to at least one mole of hexamethylenetetramine in the presence of sufficient acid to maintain the pH of the mixture not greater than 2, cooling the resulting reaction mixture to precipitate bis(trinitroethyl)amine, and recovering said bis(trinitroethyl)amine.

2. A process for making bis(trinitroethyl) amine which comprises preparing an aqueous suspension of an alkali metal salt of nitroform, mixing said salt suspension with hexamethylenetetramine in a ratio of six moles of salt to at least one mole of hexamethylenetetramine in the presence of sufficient acid to maintain the pH of the mixture not greater than 2, cooling the resulting reaction mixture to precipitate bis(trinitroethyl)amine, and recovering said bis(trinitroethyl) amine.

3. A process for making bis(trinitroethyl) amine which comprises preparing an aqueous suspension of a nitroform compound having the formula M-C(NO wherein M is a member of the group consisting of H, Li, Na, K, and NH.;, mixing said nitroform compound with hexamethylenetetramine in a ratio of six moles of nitroform compound to at least one mole of hexamethylenetetramine in the presence of a strong mineral acid to maintain the pH of the mixture not greater than 2 and maintaining the mixture at a temperature of from 20 to 30 C. cooling the resulting reaction mixture to precipitate bis- (trinitroethylyamine, ethyl) amine.

4. The process in accordance with claim 3 wherein M in the nitroform compound is potassium.

5. The process in accordance with claim 3 wherein M in the nitroform compound is sodium.

6. The process in accordance with claim 3 wherein M in the nitroform compound is ammonium.

7. The process in accordance with claim 3 wherein M in the nitroform compound is hydrogen.

No references cited.

and recovering said bis(trinitro 

1. A PROCESS FOR MAKING BIS(TRINITROETHYL) AMINE WHICH COMPRISES PREPARING AN AQUEOUS SUSPENSION OF A NITRO-FORM COMPOUND HAVING THE FORMULA M-C-(NO2)3 WHEREIN M IS A MEMBER OF THE GROUP CONSISTING OF H, LI, NA, K, AND NH4, MIXING SAID NITROFORM COMPOUND SUSPENSION WITH HEXAMETHYLENETETRAMINE IN A RATIO OF SIX MOLES OF NITROFORM COMPOUND TO AT LEAST ONE MOLE OF HEXAMETHYLENETETRAMINE IN THE PRESENCE OF SUFFICIENT ACID TO MAINTAIN THE PH OF THE MIXTURE NOT GREATER THAN 2, COOLING THE RESULTING REACTION MIXTURE TO PRECIPITATE BIS(TRINITROETHYL)AMINE, AND RECOVERING SAID BIS(TRINITROETHYL)AMINE. 